[antlr-interest] Location dependent token?

[Jared Bunting]

If the three-letter words can be anything, can you just define one token 
that matches 3 uppercase letters?  Your parser should be able to tell 
what's what based on context.

maybe something like this?

expression : NUMBER SYMBOL ('/' SYMBOL)? ;

SYMBOL : A-Z A-Z A-Z ;

-Jared

Mats Ekberg wrote:
> Ok, maybe I was a bit unsharp.
> Monetary units are expressed as three-letter words; EUR GBP and so on.
> Measurement unitts are also expressed with three letters; TNE KGM and 
> so on.
>
> The only way to know which is which is where the three letters are 
> located. In one location its a monetary and another its a measurement.
>
> ok?
>
> regards
> mats
>
> mån 2008-12-29 klockan 08:10 -0600 skrev Gary R. Van Sickle:
>> > From: Mats Ekberg
>> > 
>> > Lets say a three letter word in uppercase can mean one of two 
>> > tings like:
>> > 
>> >   10  EUR
>> > where EUR means a monetary unit
>> >   
>> >   10 EUR / TNE
>> > where EUR still means a monetary unit but the three letters 
>> > TNE now means a measurement uniot.
>> > 
>> > How can that be expressed in a grammar??
>> > 
>> > /mats 
>>
>> Your question must be missing some information, because what you're asking
>> is the most basic of lexing/parsing issues:
>>
>>
>> Lexer does something like this:
>>
>> NUMBER : [0..9]+ ;
>>
>> EUR : 'EUR' ;
>>
>> TNE : 'TNE' ;
>>
>>
>> Parser does something like this:
>>
>> num_with_monetary_unit_and_optional_per_unit
>>     : NUMBER monetary_unit ('/' measurement_unit)?
>>     ;
>>
>> monetary_unit
>>     : EUR
>>     | <<whatever other monies you support>>
>>     ;
>>
>> measurement_unit
>>     : TNE
>>     | <<whatever other measurement units you support>>
>>     ;
>>
>>
>> But was that really your question?
>>
>>     
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